Summary: Nine patients (3 women), aged 29–78 years, with acute asthma were treated with the antiasthma xanthine, enprofylline, in an open-design study without a reference drug. Enprofylline was administered intravenously (i.v.) over 2 h with an exponentially decreasing concentration. This alternative infusion system was found to be simple to handle. All patients but one reached a therapeutic plasma concentration of enprofylline within 20 min, but with a lower peak plasma concentration as compared to what previously has been found with a conventional i.v. injection of the same amount of drug. The plasma concentration of enprofylline remained on a stable and therapeutic level over the 2-h observation period. The effect on lung function was comparable to that found in other controlled trials with enprofylline. A system for i.v. administration of drugs with an exponentially decreasing concentration as an alternative to manually given i.v. injections should be further evaluated.